The biggest limiting factor in crop yields across the world is abiotic stress, causing an average loss of more than 50% of potential yield (Boyer, J. S. (1982), “Plant Productivity and Environment” Science 218(4571): 443-448). Abiotic stresses include temperature extremes, salinity, acidic soils, high light intensities, drought and combinations thereof.
As plants are sessile and cannot escape these stress conditions, they respond by changing their protein and metabolite composure, morphology and physiology. These changes allow the plant to limit damage by adapting to the stress conditions and also to repair damage caused by the stress.
These changes are mediated by processes that sense the stress and/or its effects on the plant and activate multiple, complex signalling pathways. Different pathways are activated depending on the type of stress conditions experienced by the plant but often there is overlap and interaction between pathways. This overlap can lead to cross-tolerance, that is tolerance to multiple types of stress despite exposure to only one stress. This is important as stresses rarely occur in isolation. For example cold stress will also cause high light stress as the cold causes the metabolism of the plant to slow yet it is still able to harvest as much light energy as before. Likewise drought can cause heat stress as the stomata close to conserve water but as a result lose the cooling effect of transpiration, resulting in heat stress. Furthermore in nature the stress conditions rarely exist in isolation. In Australia it would be conceivable that a crop would experience drought and high light stress at the same time.
Although some components of stress signalling pathways have been studied, due to the complexity of stress response pathways the position of these components in the pathways and their interactions with other components is poorly understood and existing methods for improving the stress resistance of plants are accordingly limited.
Thus, there is a need for new methods for producing plants with increased stress tolerance.